The process of the present invention is intended for use in the preparation of vinyl sheet goods as surface coverings and the like, particularly floor coverings. By virtue of the superior properties of a product prepared by the present process however, the process has application in a number of other areas.
Traditionally, vinyl sheet goods for use as floor coverings and the like have been prepared by coating a backing web or substrate with a liquid resinous polymeric composition which is processed into the flooring material. A useful description of the process appears in U.S. Pat. No. 3,293,094 to Nairn, Harkins, Ehrenfeld and Tarlow. Some kind of substrate is necessary during the processing of the liquid resinous composition, and may be integrated into the final product or stripped away. If the substrate is included in the final product it will add strength and dimensional stability.
For some years the material most commonly employed for this substrate was a petrochemical impregnated asbestos fiber mat. However, asbestos has recently been linked to various health hazards and its continued availability as a raw material for the asbestos felts useful for this purpose is questionable.
Research into various alternative materials which can be employed for this purpose has been carried out, but most of the materials tested have been functionally unsuitable. Others, showing marginal technical success, would have required extensive and costly changes to process equipment in order to implement their use.
For reasons of economy, one of the avenues explored was the creation of a composite mat by impregnating a fibrous mat with the printable resinous polymeric material itself. While the initial testing on conventional machinery was successful in producing a composite mat with a printable surface, irregular variations in the thickness of the gelled polymer were encountered. Where foamable plastisol was used, these irregular variations were magnified in further processing of the material, particularly where such further processing resulted in incomplete foaming of the plastisol where such irregularities were located. Further, the opposite surface was often uneven with errant, non-encapsulated fibers, which would obstruct proper adhesion in flooring uses. An additional problem encountered was incomplete interstical filling of the mat.
U.S. Pat. No. 4,138,521 to Brown shows a substrate for vinyl floor coverings which comprises a smooth, non-woven tissue of glass fibers bonded within a synthetic binder. At least one surface of the substrate contains a continuous layer of resin at least partially impregnating into the surface. This reference does not contemplate the use of a foamable plastisol and the process described would not seem to be useable for this purpose. Since the depth to which the resin impregnates the tissue is not controlled, wide variations in thickness would be expected when the material were foamed. Further, no attempt is made to encapsulate the glass tissue as in the process of the present invention. Rather, the second surface would be separately coated with a layer of resin in a repetition of the demonstrated process. Without some additional teaching with respect to how all voids in the tissue could be filled, a teaching unnecessary to the use of non-foamed resins with which the reference is concerned, the process could not be made applicable to foamable plastisols.